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<h3><a name="SECTION00161412000000000000000"></a><a name="ctypes-accessing-functions-from-loaded-dlls"></a>
<br>
14.14.1.2 Accessing functions from loaded dlls
</h3>

<p>
Functions are accessed as attributes of dll objects:
<div class="verbatim"><pre>
&gt;&gt;&gt; from ctypes import *
&gt;&gt;&gt; libc.printf
&lt;_FuncPtr object at 0x...&gt;
&gt;&gt;&gt; print windll.kernel32.GetModuleHandleA # doctest: +WINDOWS
&lt;_FuncPtr object at 0x...&gt;
&gt;&gt;&gt; print windll.kernel32.MyOwnFunction # doctest: +WINDOWS
Traceback (most recent call last):
  File "&lt;stdin&gt;", line 1, in ?
  File "ctypes.py", line 239, in __getattr__
    func = _StdcallFuncPtr(name, self)
AttributeError: function 'MyOwnFunction' not found
&gt;&gt;&gt;
</pre></div>

<p>
Note that win32 system dlls like <code>kernel32</code> and <code>user32</code> often
export ANSI as well as UNICODE versions of a function. The UNICODE
version is exported with an <code>W</code> appended to the name, while the ANSI
version is exported with an <code>A</code> appended to the name. The win32
<code>GetModuleHandle</code> function, which returns a <em>module handle</em> for a
given module name, has the following C prototype, and a macro is used
to expose one of them as <code>GetModuleHandle</code> depending on whether
UNICODE is defined or not:
<div class="verbatim"><pre>
/* ANSI version */
HMODULE GetModuleHandleA(LPCSTR lpModuleName);
/* UNICODE version */
HMODULE GetModuleHandleW(LPCWSTR lpModuleName);
</pre></div>

<p>
<var>windll</var> does not try to select one of them by magic, you must
access the version you need by specifying <code>GetModuleHandleA</code> or
<code>GetModuleHandleW</code> explicitely, and then call it with normal strings
or unicode strings respectively.

<p>
Sometimes, dlls export functions with names which aren't valid Python
identifiers, like <code>"??2@YAPAXI@Z"</code>. In this case you have to use
<code>getattr</code> to retrieve the function:
<div class="verbatim"><pre>
&gt;&gt;&gt; getattr(cdll.msvcrt, "??2@YAPAXI@Z") # doctest: +WINDOWS
&lt;_FuncPtr object at 0x...&gt;
&gt;&gt;&gt;
</pre></div>

<p>
On Windows, some dlls export functions not by name but by ordinal.
These functions can be accessed by indexing the dll object with the
ordinal number:
<div class="verbatim"><pre>
&gt;&gt;&gt; cdll.kernel32[1] # doctest: +WINDOWS
&lt;_FuncPtr object at 0x...&gt;
&gt;&gt;&gt; cdll.kernel32[0] # doctest: +WINDOWS
Traceback (most recent call last):
  File "&lt;stdin&gt;", line 1, in ?
  File "ctypes.py", line 310, in __getitem__
    func = _StdcallFuncPtr(name, self)
AttributeError: function ordinal 0 not found
&gt;&gt;&gt;
</pre></div>

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